Proceedings Paper

Light demultiplexing plays an important role in optical fiber communications. A lot of efforts have been devoted recently to manufacture a device that combines high efficiency, flat spectral response, and low production costs. The contribution discusses the difficulties due to the influence of the polarization effects on diffraction grating properties. The deviations of the ideal profile during the manufacturing process are also responsible to degrade the efficiency. While standard echelettes (triangular-groove gratings) can provide high efficiency in non-polarized light for low-blazed angles, they are not suitable due to the weak angular dispersion leading to large device dimensions. Higher-angle echelettes have the required angular dispersion for device dimensions of, typically, 10 to 15 cm, but electromagnetic effects lead to strong polarization dependence. Photonic crystals, consisting of rods or holes and working in the forbidden region can provide flat spectral response and no polarization dependence.